Electric control system



Feb. 20, 1940. E. E. MOYER ELECTRIC CONTRQL SYSTEM 3 Sheets-Sheet l Inventor:

Filed April 17, 1937 O Q t M me E Feb. 20, 1940. E. E. MOYER 2,190,756

ELECTRIC CONTROL SYSTEM Filed April 17, 1937 3 Sheets-Sheet 2 Ihvehtor: Elmo E. ["10 er,

H IS Attorney.

Feb. 20, 1940. MQYER 2,190,755

ELECTRIC CONTROL SYSTEM Filed April 17, 1937 3 Sheets-Sheet 3 Inven t or Elmo ElMo en JQL Hi S Attorney.

. Patented Feb. 20, 1940,

2,190,756 ELECTRIC CONTROL SYSTEM Elmo E. Moyer, Scotia, N. Y., assig'nor to General Electric Company, a corporation of New York Application April 17, 1937, Serial No. 137,525

Claims.

of synchronous machines, attention has been diill rected to the problem of increasing the power limits of the machines to improve the stability of the associated electric power systems.

In view of these factors there has been evidenced a decided. need for arrangements to in-,

i5 crease the steady state power limits of synchronous machines so that the machines may operate to supply overloads without falling out of synchronism with the associated system. Moreover, it is important that the synchronous ma- 20 chines be capable ofassuming the increase in load in practical simultaneity with such increase so that the continuity of service is not disturbed.

It is an object of my invention to provide a new and improved control system for dynamo- 25 electric machines.

It is another object of my invention to pro-' vide a new and improved electric valve system for increasing the steady state power limit of dynamo-electric machines of the synchronous 30 type.

It is a further object of my invention to provide a new and improved electric valve translating system. I

In accordance with the illustrated embodi- 35 ments of my invention, I provide improved electric valve control systems shown as applied to arrangements for increasing the steady state power limit of dynamo-electric machines of the synchronous type. In particular, I provide elec- 40 tric valve circuits for supplying direct current to the armature windings of a dynamo-electric machine to cause said machine to operate higher up on the saturation curve, thereby increasing the steady state power limit of the machine. As

5 will be understood in view of the various embodiments described hereinafter, this control of the dynamo-electric machine to increase the steady state power limit may be accomplished in a variety of ways. The electric valve apparatus may cult to control the current supplied to the armature windings. A circuit controlling means such asa switching device may be interposed between the armature windings and the electric valve means to connect selectively and disconnect the 5 electric valve means to accomplish the control of the magnetic condition of the core member in accordance with machine or circuit conditions.

In one embodiment of my invention one group p of electric valve means is connected to the mal0 chine terminals and to the field winding to supply direct current to the field winding and to the armature windings, and a second group of electric valve means is associated with the first group and with the machine to control the component of direct current supplied to the armature windings in accordance with the alternating component of current in the armature windings.

My copending patent application Serial No. 158,559 filed August 11, 1937 is a division of this application and discloses and broadly claims cer-' tain features of the electric valve circuits shown in this application.

Fora better understanding oi. my invention. reference may be had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims. Fig. 1 of the accompanying drawings diagrammatically illustrates my invention as applied to a dynamo-electric machine of the synchronous type in which a controlled rectifier supplies current to the armature windings; Figs. 2, 3 and 4 diagrammatically show other embodiments of my invention in which the control of the current transmitted to the armature windings is effected by electric valve means differently arranged. Fig. 4a shows a simplified diagrammatic circuit corresponding to Fig. 4.

Fig. 1 of the accompanying drawings diagrammatically illustrates an embodiment of my invention as applied to a dynamo-electric machine I of the synchronous type having armature phase windings 2, 3, and 4 provided with a neutral connection 5, an associated core member or structure 5 and a relatively movablefleldhinding 6. The armature windings2, 3 and 4 are connected to an alternating current circuit 1 which may function as either a supply circuit or a load circuit. An exciter is connected to the field winding 6 I to supply direct current thereto and includes an armaturemember 8 and a field winding 9. A sub-exciter l0 may be employed to control the energization of the field winding 9 of the maln exciter.

An excitation system II is associated with the 18 and I9.

main exciter and the sub-exciter I to control the energization of the field winding 6 in accordance with an electrical condition such as the voltage of the alternating current circuit 1 or in accordance with the terminal voltage of the armature windings of the dynamo-electric machine I While for the purpose of explaining my invention I have chosen to represent the excitation system as being of the vibratory type, it should'be understood thatI may employ any other conventional voltage regulating device for controlling the energization-of the field winding 6 in accordance with a predetermined electrical condition. The excitation system Il .may include a voltage responsive 'coil 12 energized from the alternating current circuit 1 through a transformer I3, a system of vibratory cooperating contacts l4 and an actuating coil I which is responsive to the armature voltage of the subexciter Ill. It will be undestood by those skilled in the art that the actuating coil l2 may be made responsive to polyphase voltage conditions of the alternating current circuit 1 so that the excitation system H of machine I may be properly controlled under unbalanced operating conditions; The excitation system serves to intermittently short circuit a resistance I6 connected in the field circuit of the sub-exciter III to control the voltage thereof in accordance with the voltage of the circuit 1.

In order to supply direct current to armature windings 2, 3 and 4 of dynamo-electric machine I to cause the machine to operate higher up on the saturation curve, I provide a plurality of electric valve means l1, I8 and 19 which are connected between different armature windings and the neutral connection 5 thereof through a smoothing inductive reactance' 20. The electric valve means I1, [8 and 19 are preferably of the type employing an ionizable medium such as a gas or a vapor and each includes an anode 2|, a cathode 22' and a control member 23 for controlling the conductivity of the associated discharge path. Smoothing inductive reactance 24 may also be connected in series relation with the electric valve means 51,

As an agency for controlling the conductivities of the electric valve means l1, Ill and 19 in accordance with a predetermined electrical conditionof the alternating current circuit 1 or in accordance with a predetermined electrical condition of the armature windings 2, 3 and 4 of machine I, I provide a control circuit 25 which is responsive to the current of the alternating current circuit 1. A suitable inductive device such as a current transformer 26 may be associated with each' of the conductors of the circuit 1 to provide an alternating voltage which varies in accordance with the current, and a circuit 21 is used to provide a unidirectional voltage which varies in accordance with the current of the alternating current circuit 1. The circuit 21 may include a full wave rectifying device 28, an adjustable resistor 29 connected across the terminals of the current transformer 26, an impedance element such as a resistance 30 and a capacitance 3| connected in parallel relation with the resistance 30. It will be understood by those skilled in the art that the control or the electric valves l1, l8 and I9 may be made responsive to polyphase conditions of the alternating current circuit 1; for example, the currents in the various conductors of circuit 1 may be summated or inte grated by well known'arrangements to control the electric valves I1, 18 and I9 in'accordance with the polyphase current conditions. To impress on control members 23 of electric valve means 11, I8 and I9 alternating voltages adjustable in phase, I employ a transformer 32 having primary windings 33 and secondary windings 34 which are connected to control members 23 through current limiting resistances 35. Connected in series relation with the resistance 30, I employ a suitable source of negative unidirectional biasing potential such as a battery 36 which introduces in the control circuit 25 a potential which acts in opposition to the voltage provided by the resistance 30 and the associated circuit 21. The magnitude of the potential provided by battery 35 may be' chosen so that it is sufficiently-large to maintain the electric valve means l1, l8 and I9 nonconductive within a predetermined range of current in the circuit 1, and the circuit 21 may be energized to provide a voltage to render ineffective or neutralize the potential of battery 26 when the current of circuit 1 increases beyond a predetermined value, so that the conductivities of electric valves l1, l8 and I9 are controlled to supply a unidirectional component of current to armature windings 2, 3 and 4 of machine I in accordance with the alternating component of current of the armature windings. Any suitable phase shifting arrangement, as a rotary phase shifting device 31, may be employed to control the phase of the alternating voltage introduced in control circuit 25 by transformer 32.

The operation of the embodiment of my invention diagrammatically shown in Fig. 1 will be explained by considering the system when the dynamo-electric machine I- is operating as a synchronous generator to supply alternating current to the circuit 1. Let it be assumed that the control circuit 25 is adjusted so that the unidirectional biasing potential provided by the battery 36 is sufficiently great to maintain the electric valve means l1, l8 and i9 nonconductive within a predetermined range of current transfer between the armature windings 2, 3 and 4 of machine I and the alternating current circuit 1. As the current varies within this range of values, the excitation system II will respond to control the energization of field winding 6 so that the voltage of the alternating current circuit 1 is maintained at a predeterminedv value. If it be assumed further that the current supplied by the machine I increases to a value above said predetermined range of values, the voltage appearing across the terminals of resistance 30 will become sufliciently large so that the resultant unidirectional voltage acting in the control circuit 25 is reduced to render electric valves I1, l8 and I9 conductive at a predetermined time during the respective positive half cycles of anode voltage. to produce unidirectional components of current in the armature windings 2, 3 and 4. The rotary phase shifter 31 may be adjusted so that the alternating voltages introduced in the control circuit 25 have a predetermined lagging relationship relative to the voltages impressed on anodes 2| of electric valve means l1, l8 and I9 so that as the resultant unidirectional voltage actingin circuit 25-becomes less negative the conductivities of electric valves l1, l8 and I9 will be correspondingly increased to control the direct current supplied to armature windings 2, 3 and 4 in accordance with the alternating component of current in these windings.

It is understood that the steady state power output of a dynamo-electric machine of the synchronous type is directly proportional to the product of the terminal voltage, the voltage correvoltages and is inversely proportional to the synchronous reactance of the machine. This gen- .eral statement represents the power oi the machine neglecting the double frequency component of power due to the difference in the reactances in the ,direct and quadrature axes of the machine. However, for general purposes the above .relatiom ship defines the power with suiiicient accuracy. Since'the maximum power output of the machine occurs when the derivative of the power with respect to the displacement angle is zero, the maximum power output is obtainable when the'displacement angle is slightly less than ninety electrical degrees.

The arrangement of Fig. 2. is similar to that of Fig. 1 and corresponding elements have been assigned like reference numerals. In this figure there is. disclosed another embodiment of my invention in which direct current is supplied to the armature windings by means of electric valves 38, 3! and '40, preferably the type emplaying an ionizable medium such as a gas or a vapor, and which are associated with controlling means such as-saturable reactors 4|, 42 and" i'or controlling the impedance of the respective anode-cathode circuits 01 these valves. Each oi? the saturable reactors 4I', 41 and 43 may include a winding 44 connected in series with thems- 'sociated electric valve and. a control winding 45 which controls the impedance of the series winding 44. An electric valve circuit 48 including electric valves 41 and '48, which may be ener-f gized from any suitable source of alternating current, is employed to supply'direct current to control windings 45 of saturable reactances 4|, 42 and 43 inaccordance with the current of the alternating current circuit I, or in accordance with the current of armature windings 2, I and 4 of machine I. In the particular arrangement shown in the drawings, the electric valve circuit 46 is shown as being energized from the circuit I through a transformer 49, and it is to be understood that the circuit 46 may be energized from any other suitable source of current. Electric valves 41 and 48 are provided with control members 50 which are energized by a control circuit including a transformer 52 which impresses alternating voltages on the control members 50 through current limiting resistances 53. The transformer 52 may be energized through any suitable phase shifting arrangement such as a rotary phase shiiter U4.

The operation of the embodiment of my invention diagrammatically shown in Fig. 2 is substantially the same as the operation of the embodiment of my invention shown in Fig. 1. Let it be assumed that machine I is operating as a synchronous generator to transmit energy to the alternating current circuit I and let it be assumed that the circuit SI is adjusted so that the current supplied to control windings 4! ct saturable reactors 4|, 42 and 43 by circuit 4' is substantially zero within a predetermined range of current in the alternating current circuit 1. Under these conditions, the impedance of the series windings 44 of saturable reactors H, 42 and 43 will be relatively large so that there will be practically no unidirectional current in the armature windings 2, 3 and 4 0! machine I. As the current of the circuit 7 or as the current of the machine II increases to a value beyond this range of values, the voltage provided by resistance 30 oi circuit 2i will be increased to eiiect a reduction in the negative potential acting in circuit II to increase the conductivities of electric valves 41 and 4., causing these valves to supply current to control windings 4l 0! the saturable reactors 4|, 42 and 43. As a result, the impedance of the series windings 44 will be decreased thereby permitting the electric valves 38, 39 and 40' to supply a relatively large component of direct current to the armature windings 01 machine I; causing the machine I to operate higher up on the saturation curve and producing thereby an increase in the steady state power limit of machine I. It is to be understood that the excitation system I I will under all conditions respond to control the *energization of the iield winding 6 to maintain the terminal voltage of machine I substantially constant.

Referring now to Fig. 3 of the accompanying drawings, there is diagrammatically represented another embodiment of my invention for eflecting control of the steady state power limit of dynamo-electric machine I in which a circuit controlling means is interposed between the electric valvemeans and the armature windings of the machine selectively to open and close the electric valve circuit. Various elements in the arrangement shown in Fig. 3 correspond to elements shown in Figs. 1 and 2 and have been assigned like reierence numerals. I

In order to eil'ect selective control of the unidirectional componentoi current in the armature windings 2, 3 and 4 of machine I, I employ a suitable circuit controlling means such as a circuit interrupter 55 including a movable contact member 56 biased to the open circuit position, stationary contacts 51, a closing coil 58 and a tripping coil 59. A suitable unidirectional conducting device such as a contact rectifier 60 may be connected 'in parallel with the closing coil to assure that the closing coil of circuit interrupter .55 is energized with only current of a predetermined polarity. In order to effect energization of the closing coil 58 to establish a unidirectional component of current in the armature windings 2, 3 and 4 when the current oi the alternating current circuits I increases beyond a predetermined value, I employ a circuit 8| including a controlled electric valve 62 preferably of the type employing an ionizable medium and having a control member 63 which is energized in accordance with the difierence in the voltage provided by the battery as and the circuit 21. A-current limiting resistance 84 may be connected in series relation with the control member l3 0! electric valve S2. A relay i! having an actuating coil 68 and an armature mem- A resistance 69 is the machine I is operating as .a synchronous generator to supply current to the circuit I. The excitation system -II will operate to control the energization oi! the field winding 6 so that the terminal voltage of machine I is maintained at a substantiallyconstant value. Let it be assumed that the circuit 2! is adjusted to provide a voltage such that the unidirectional negative biasing potential provided bythe battery 36 predominates to impress a negative potential on the control member '63 of electric valve .62 to maintain the electric valve 62 nonconductive within a predetermined'range of current of the circuit 1. Under these conditions the circuit interrupter 55 will be maintained in the open circuit position so that no direct current is supplied to the armature windings 2, 3 and 4 of machine I. If the current of the circuit 1 increases beyond a predetermined value or, in other words, if alternating current supplied by armature windings 2, 3 and 4 of machine I increases by a predetermined value, the positive voltage provided 'by resistance 30 will predominate, impressing on control member 83 of electric valve 82 a positive voltage to render electric valve 82 conductive. The voltage appearing across the terminals of resistance 69 will be sufiicient to raise the armature member 61 of relay 65 to interrupt the circuit for the tripping coil 59 and the current supplied by circuit 6| will energize the closing coil 58 of circuit interrupter 55 to connect electric valves 38, 39 and 40 to the neutral connection 5 of the armature windings of machine I. As a result thereof, a unidirectional component of current of a predetermined magnitude established by the design of the associated circuit will be established in armature windings 2, 3 and 4 to cause the machine to operate higher up on the saturation curve. If the current of the circuit 1 or of the armature winding of machine I decreases below the predetermined value, the negative biasing potential provided by battery 36 will predominate over the positive voltage provided by resistance 30 to render electric valve 82 nonconductive, thereby effecting deenergization of the closing coil 58 and closing relay B5 to trip circuit interrupter 55 by energizing the trip coil 59. In this manner the system operates selectively to open and close the circuit including electric valves 5 38, 39 and 40 to control the steady state power limit of the machine inv accordance with the current in circuit 1 or in accordance with the current in the armature windings.

Referring now to Fig. 4 of the accompanying drawings, there is diagrammatically shown another embodiment of my invention for controlling the steady state power limit of a dynamo-electric machine of the synchronous type. One group of electric valve means comprising electric valves 10, H and 12 is connected across the terminals of the armature windings 2, 3 and 4 and to one terminal of the field winding 6. The other terminal of the field winding 8 is connected to the electrical neutral connection 5 of the armature windings. Each of the electric valves 10, H and 12 is provided with a control member 13 for controlling the conductivity of the associated discharge path and electric valves 10, H and 12 are preferably of the type employing an ionizable medium such as a gas or a vapor. In order to provide a system of voltages 180 electrical degrees out of phase with the terminal voltages of armature windings 2, 3 and 4, I provide an inductive network 14 comprising windings 15, which are connected to the terminals of armature windings 2, 3 and 4, and a plurality of windings 16 having output terminals which are connected to a second group of electric valves 11, 18 and 19. The inductive network 14 is also provided with a neutral terminal 16' which is connected to the neutral connection 5 of armature windings 2, 3 and 4. The electric valves 11, 18 and 19 are also preferably of the type employing an ionizable medium such as a gas or a vapor and each includes a control member for controlling the conductivity of the associated discharge path. 'I'he'cathodes of electric valves 11, 18 and 19 are connected to the cathodes of electric valves 10, H and 12.

' I provide a control circuit 8| for impressing on the control members 13 of electric valves 10, 11 and 12 and control members 80 of electric valves 11, 18 and 19 alternating voltages variable in phase to maintain the voltage of armature windings 2,3 and 4 at a substantially constant value and for controlling the electric valves to supply direct current to the armature windings when the load of the machine I increases beyond a predetermined value. The control circuit BI comprises a plurality of inductive devices 82, 83 and 84, each of which includes a core member arranged to provide two control voltages. Inductive device 82 is associated with electric valves 10 and 11; inductive device 83 is associated with electric valves H and 18, and inductive device 84 is associated with electric valves 12 and 19. Inductive devices 82, 83 and'84 are provided with exciting windings 85, 86 and 81, respectively, which are energized each in accordance with the voltage of one phase of the three phase alternating current circuit. This source of alternating current may be derived from any suitable source and in the arrangement shown in the drawings is obtained from the alternating current circuit 1 through any conventional phase shifting arrangement such as the rotary phase shifting device.88. The inductive devices 82, 83 and 84 are also provided with-unidirectional biasing windings 89, 90; 9I, 92; 93, 94, respectively. These windings serve to impress on the associated core members unidirectional magnetomotive forces of substantially constant value. The inductive devices 82, 83 and 84 are also provided with unidirectional biasing windings 95, 90; 91, 98; 99, I00,

respectively. The latter mentioned windings are arranged on the respective core members of inductive devices 82, 83 and 84 to oppose the effect of the unidirectional magnetic biasing windings 8994, inclusive. Control windings IOI, I02;' I03, I04; I05, I06, are associated with inductive devices 82, 83 and 84 respectively, to provide alternating voltages variable in phase to control the conductivities of the associated electric valve means. Current limiting resistances I01 may be connected in series relation with the associated control members. Unidirectional conducting devices I08 are connected across the control windings associated with each of the inductive devices 82, 83 and 84 to short circuit the control winding which is providing a negative voltage in order to assure that the winding producing a positive voltage is interlinked with a sufficient flux to provide the desired positive voltage. If desired, the core members of inductive devices 82, 83 and 84 may be arranged so that the voltages induced in the control windings are of a peaked Wave form.

I provide a voltage sensitive circuit I09 comprising a transformer IIO having primary windings II I connected to the terminals of the armature windings 2, 3 and 4 and having a plurality of secondary windings II2. A rectifier comprising a plurality of electric valves I I3 serves to provide a source of unidirectional voltage II4 the magniinductance II5 may be connected in series rela- 75 tion with the associated secondary windings H2 and the electric valves I I8 and a capacitance H8 is connected across the output circuit of the rectiller. In order to provide a substantially constant unidirectional voltage, I provide a serially connected glow discharge valve Ill and resistance' II8 which are connected in parallel with 'the capacitance IlIi. The voltage appearing across the glow discharge valve III supplies a control current of substantially constant magnitude tobiasingwindings 88-84 oi inductive devices 82, 83 and 84 and also serves to impress a negative unidirectional biasing potential of substantially constant value on control members 18 of electric valves I0, II and I2 and on control members of electric valves 'II, I8 and I8 through a circuit including a conductor II8, a conductor I20 and the associated control windings. A voltage divider including a resistance i2I having an adjustable contact I22 is connected in parallel with the serially connected glow discharge valve II! and resistance II8-and serves to provide an adjustable voltage which varies in accordance with the voltage of the armature windings of the machine 8 to energize biasing windings 85, 81 and 89 of inductive devices 82, 83 and 84, respectively, to control the conductivities of electric valves 10, II and I2 in accordance with the voltage of the armature windings. A resistance I23 may be connected in series relation with the adjustable contact I22 of the voltage divider and biasing windings 85, all and 88.

I provide a current or load responsive circuit i124; including a plurality of current responsive devices such as current transformers 28 and associated rectifiers I25 for providing a unidirectional voltage, the magnitude of which varies in accordance with the current of the three phases oi the alternating current circuit I, or in accordance with the current of the three phases at "the armature windings of machine I. A smoothing reactor I26 may be connected in series relation with the rectifiers I25 and a capacitance it?! may be connected across the output circuit of the rectifiers E25 to serve as an energy storage device. The positive terminal of capacitance I2I is connected to the movablecontact I22 of the voltage divided through a unidirectional conducting device l28having an anode I28 and a cathode I30. 'The positive terminal of capacitance 821 is also connected to biasing windings 98, 88 and I 00 of inductive devices 82, 83 and 84 to control the energiz'ation of these windings in accordance with the current or load of the alternating current circuit I or in accordance with the current or load of the machine I.

Before explaining the general prinicples of operation of the embodiment .of my, invention diagrammatically shown in Fig. 4, the operation at the various individual circuits will be explained. Considering the electric valves 10, ll, 52, W, I8 and I9, it will be understood by those skilled in the art that when these valves are of the type employing an ionizable medium the control members are effective to maintain the electric valves nonconductive and that after the valves have been rendered conductive by impressing on the control members a sufliciently positive voltage, the electric valves may be rendered nonconductive only by impressing on the associated anodes a potential sufliciently negative relative to that of the cathode for a time equal to or greater than the time of deionization of the valves. The voltages impressed on the control members I8 of electric valves II, II and I2 and control members 80 of electric valves 11, I8 and I8 comprise a unidirectional negative biasing potential of substantially constant value provided by the glow'discharge valve Ill and the,

alternating voltages of peaked wave form provided by control windings IOI- I08, of inductive devices 82, 83 and 84. Considering one of the inductive devices in particular, as for example inductive device 82, it is to be understood that the voltages provided by control windings IM and I02 are eletrical degrees out of phase with respect to each other, and that these voltages tend to render the associated electric valves I0 and 11, respectively, conductive during intervals displaced 180 electrical degrees. Biasing windings 85, 81 and 88 of inductive devices 82, 88 and 84, respectively, are arranged to oppose the magnetomotive forces established by windings 88, 9| and 83 to control the phase of the alternating voltages of peaked wave form induced in control windings IOI, I03 and I05 in accordance with the magnitude of the armature voltage of machine I. windings 88-84, inclusive, establish in the respective core members of inductive devices 82, 83 and 84 unidirectional magnetomotive forces tending to advance the phase of the control voltages provided by control windings IOI-I05 to the full-on position. Upon increase in armature voltage of machine I, the incident increase in energization of windings 85, 81 and 88 will effect a retardation in phase of the voltages induced in control windings IOI, I08 and I05 to decrease the conductivities of electric valves 10, H and I2 and to thereby efiect a decrease in the energization of the field winding to return the armature voltage oi machine I to the predetermined value to be maintained. In like manner the energization of windings 88,88 and I00 01' inductive devices 82, 83 and 84 will control the phase of the voltages induced in control windings I02, I04 and I06 to control the conductivities 01 electric valves l1, l8 and I8 within a predetermined range of current or load of the \machine l or of the alternating current circuit I.

It is to be understood that the voltage sensitive circuit I08 will provide a unidirectional voltage the magnitude of which varies in accordance with the voltages of the three phases of the armature windings of machine I, or in accordance with the voltage of the alternating current circuit I. By virtue of the characteristics of the glow discharge valve HI,'the voltage appearing across its terminals will be substantially constant and by the proper adjustment of the movable contact I22 of the voltage divider there is provided means to obtain a component of voltage of the output circuit I I4 which varies in accordance with the voltage of machine I.

Within a predetermined range of current supplied by the machine I to the alternating current circuit I, the electric valves 10, II, I2, 11, I8 and I8 will be controlled to operate as a six-phase rec. tifler to supply unidirectional current to the field winding 8 to maintain the armature voltage at a substantially constant value, and no unidirectional component will exist in the armature windings 2, 3 and'4 since the current is conducted from the neutral connection 5 of these windings to the neutral terminal I8 of the inductive network I4 through the neutral connection. However, as the current supplied to the alternating current circuit I increases beyond a predetermined value, the voltage supplied by the circuit ages of windings I02, I04 and I06 to render'electric valves 11, I8 and I9 conductive for progressively smaller intervals during each cycle. Within this range of current transfer where the voltages impressed on control members 80 of electric valves 11, I8 and I9 is progressively retarded in phase, it is to be understood that the rate at which the saturation of the core member is accomplished relative to the current of the ar- ,mature windings may be'controlled by adjustment of the movable contact I22 of the voltage divider and by the adjustment of other features of the control circuit 8|. At a second predetermined value of current transfer above the first value, it will be understood that by virtue of the increase in voltage of capacitance I21 and incident energization of windings 96, 98 and I00, the voltages impressed on control members 80 of electric valves 11, I8 and 19 will be retarded sufficiently to maintain these electric valves nonconductive so that the electric valves I0, II and I2 operate as a three phase half wave rectifier. For values of current above the second predetermined value, electric valves 11, I8 and I9 are controlled predominantly. in accordance with the current. Under this condition of operation, an appreciable direct current is conducted through armature windings 2, 3 and 4 to cause said machine to operate higher up on the saturation curve and to increase the steady state power limit of machine I.

The simplified diagram of Fig. 41; will be of assistance in explaining the general principles of operation of the embodiment shown in Fig. 4. The elements of the circuit of Fig. 4a have been assigned reference numerals corresponding to the respective elements of Fig. 4. Within a predetermined range of current transfer, the system will respond to control the energization of the field winding 6 in accordance with the armature voltage of machine I or in accordance with the voltage of the alternating current circuit I since control windings 95 -100, inclusive, are connected to be energizedg in accordance with a unidirectional voltage which varies in accordance with the voltage to be regulated, that is, connectedtqgbe ergized in accordance with a predetermined co popent of the voltage appearing acrossresistance I2I of the voltage divider. So long as the current transmitted does not exceed a predetermined value to increase the volt-' age of capacitance I21 too greatly, the voltage provided by resistance I2I through movable contact I22 will control the energization of windings 96, 98 and I of inductive devices 82, 83 and 84 in accordance with the voltage of the circuit. In other words, the electric valves 11, I8 and I9 as well as electric valves I0, II and I2 will be controlled in' accordance with the armature voltage of machine I. However, as the current transmitted ekceeds the predetermined range of values, the voltage impressed on control members 80 of electric valves 11, I8 and I9 will be retarded in phase to decrease the conductivities of these valves. During this state of operation, the voltage of the machine I will be maintained at a constant value by virtue of the control of electric valves I0, II and 12 through windings 95, 91 and 99 of inductive devices 82, 83 and 84. As the currenttransmitted obtains a second predetermined value above the range of values, the windings 96, 98v and I00 will be energized to retard I0, II and I2 control the energization of the field winding of machine I to maintain the armature voltage thereof at a substantially constant value and since these valves are operating as a half Wave rectifier, the unidirectional component of current conducted through windings 2, 3 and 4 will cause the machine to operate higher up on the saturation curve, effecting thereby a material increase in the steady state power limit of the machine.

While I have shown and described my invention as applied to a particular system of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

' with an electrical neutral connection, an associated core member and a relatively movable field winding, an excitation system for controlling the energization of said field winding in acccordance with the voltage of said armature windin a plurality of electric valve means connected between diiferent phases of said armature windin and said neutral connection for establishing a unidirectional component of current in said winding, a plurality of saturable reactors each connected in series relation with a different one of said electric valve means for controlling the current conducted by said electric valve means and each including a control winding for controlling the impedance of said saturable reactors, and means responsive to the current of said armature winding for controlling the current supplied to said control winding to effect control of the unidirectional current in said armature winding. 1

2. In combinatioh; a polyphase alternating current circuit, a dynamo-electric machine of the synchronous type having a plurality of phase windings connected thereto and being provided with an electrical neutral connection, an associated core member and a relatively movable field winding having a pair of terminals one of which is connected to said neutral connection, a group of electric valve means each being connected to a different one of said phase windings,

winding, and means for controlling said first mentioned group of electric valve means and said What I claim as new and desire to secure by current circuit, a dynamo-electric machine of the synchronous type having a plurality of phase windings connected to said circuit and provided with an electrical neutral connection, an associated core member and a relatively movable field winding having a pair of terminals one of which is connected to said neutral connection, a group of electric valve means each being connected to a different one of said phase windings and to the other terminal of said field winding, an inductive network comprising a plurality of windings connected to said phase windings and having output terminals for providing a system of voltages 180 electrical degrees out 01' phase with the terminal voltages of said phase windings and a neutral terminal connected to said neutral connection of said phase windings, a second group of electric valve means connected to said output terminals and 'said other terminal of said field winding, means for controlling said first mentioned group and said second group of electric valve means in accordance with the voltage of said phase windings to control the energization of said field winding within a predetermined range of current of said phase windings, and means for rendering said second group of electric valve means nonconductive when the current of said phase windings exceeds a predetermined value to cause said first mentioned group of electric valve means to establish a unidirectional component of current in said armature phase windings.

4. In combination, a polyphase alternating current circuit, a dynamo-electric machine 'of the synchronous type having a' plurality of phase windings connected thereto and being provided 40 with an electrical neutral connection, an associated core member and a relatively movable field winding having a pair of terminal connections one of which is connected to said neutral connection, a group of electric valve means each being connected to a different one of said phase windings and to the other terminal or said field winding for supplying direct current to said field winding through said neutral connection, an indiictive network comprising a plurality of wind ings connected to said phase windings and having output terminals for providing a system of voltages 180 electrical degrees out of phase with the terminal voltages of said phase windings and a neutral terminal connected to said neutral connection of said phase windings, a second group of electric valve means interposed 'between said output terminals and said other terminal of said field winding, means for controlling said first mentioned group of electric valve means and said second group of electric valve means in accordance with the voltage of said phase windings within a predetermined range of the alternating component of current of said phase windings, means for continuously decreasing the conductivity of 5 said second group of electric valve means within a second range of current of said armature winding to cause said first mentioned group of electric valve means to supply direct current to said armature phase windings through said field wind- 70 ing to control the magnetization of said core members in accordance with the armature current and for rendering said second group of electric valve means nonconductive when the alternating component of the current in said phase 75 windings exceeds a predetermined value to increase the unidirectional component of current in said armature phase windings to a value sufficient to cause said machine to operate higher up on the saturation curve.

5. In combination, a polyphase alternating current circuit, a dynamo-electric machine of the synchronous type having a plurality of phase windings connected thereto and being provided with an electrical neutral connection, an associated core member'and a relatively movable field winding having a pair of terminal connections one of which is connected to said neutral connection, a group of electric valve means each being connected to a difierent one of said phase windings and to the other terminal of said field winding for supplying direct current to said field winding through said neutral connection, said electric valve means being provided with control members for controlling the conductivity thereof, an inductive network comprising a plurality of windings connected to said phase windings and having output terminals for providing a system of voltages 180 electrical degrees out of phase with the terminal voltages of said phase windings and a neutral terminal connected to said neutral connection of said phase windings, a second group of electric valve means interposed between said output terminals and said other terminal of said field winding and each valve comprising a control member for controlling the conductivity thereof, and a control circuit for impressing alternating voltages variable in phase relative to the voltage of said phase windings on the control members of said first mentioned group of electric valve means to maintain substantially constant the voltage of said phase windings and for controlling the phase of the voltages impressed on the control members of said second group of electric valve means to control the component of unidirectional current in said phase windings in accordance with the alternating current of said phase windings.

6. In combination, an alternating current circuit, a dynamo-electric machine of the synchronous type having armature windings connected to said alternating current circuit, an associated core member and a relatively movable field winding, a group of electric valve means connected between said alternating current circuit and said field winding for supplying direct current thereto and each electric valve means comprising a control member for controlling the conductivity fer between said armature windings and said alternating current circuit and for progressively retarding in phase the voltages impressed on the control members of said second group of electric valve means to decrease the conductivity thereof and for progressively advancing in phase the control voltages impressed on the control members of said first mentioned group of valves to control the voltage of said alternating current circuit by the energization of said field winding by said first mentioned group of valves for values of current transfer above said predeterminedrange, the respective groups of valves at any one time having different'degrees of conductivity.

'7. In combination, a dynamo-electric machine of the synchronous type having an armature winding provided with a neutral connection and a field winding having a pair 'of terminal connections one of which is connected to said neutral connection, electric valve means connected between said armature winding and the other terminal connection of said field winding for supplying direct current thereto, and means for controlling said electric valve means in accordance with the current of said armature winding.

8. In combination, a dynamo-electric machine having an armature Winding provided with a neutral connection, an excitation means therefor including a field winding having a pair of terminal connections one of which is connected to saidneutral connection, electric valve means connected between said armature winding and the other terminal of said field winding for controlling the energization of said field winding in accordance with the current of said armature winding, and voltage responsive means for additionally controlling the energization of said excitation means.

9. In combination, a dynamo-electric machine having an armature winding provided with a neutral connection and a field winding having a pair of terminal connections one of which is connected to said neutral connection, electric valve means connected between said armature winding and the other connection of said field winding for supplying direct current thereto. and means for controlling the conductivity of said electric valve means conjointly in accordance with the current and the voltage of said armature winding.

10. In combination, an alternating current circuit, an electrical network connected to said alternating current circuit and having a neutral connection, a group of electric valve means connected to said alternating current circuit and to said network, a second electrical network connected to said alternating current circuit for producing a system of alternating voltages displaced 180 electrical degrees relative to the voltages impressed on said electric valve means, said second network* being provided with a neutral connection connected to the neutral connection of said first mentioned electrical network, a second group of electric valves connected to transmit current from said circuit to said second electrical network, and an excitation circuit for controlling the conductivities of both groups of electric valve means in accordance with a predetermined electrical condition of said alternating current circuit within a predetermined range of a second electrical condition of said'alternating current circuit and means for controlling the conductivity of one of said groups of electric valve means predominately in accordance with said'second electrical condition when said second electrical condition exceeds said predetermined range to establish in said first mentioned electrical network a current having a substantial unidirectional component.

ELMOlE. MOYER. 

